From nobody Tue Feb 10 05:10:41 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1511874412245529.1310021545354; Tue, 28 Nov 2017 05:06:52 -0800 (PST) Received: from localhost ([::1]:37848 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eJfas-0002ve-Vd for importer@patchew.org; Tue, 28 Nov 2017 08:06:35 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49596) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eJfY8-0001D4-Cu for qemu-devel@nongnu.org; Tue, 28 Nov 2017 08:03:49 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eJfY2-0003hx-Hk for qemu-devel@nongnu.org; Tue, 28 Nov 2017 08:03:44 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35262) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eJfXq-0003eX-Jg; Tue, 28 Nov 2017 08:03:26 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B4829127AE; Tue, 28 Nov 2017 13:03:25 +0000 (UTC) Received: from red.redhat.com (ovpn-122-79.rdu2.redhat.com [10.10.122.79]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7BF5F605D8; Tue, 28 Nov 2017 13:03:17 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Date: Tue, 28 Nov 2017 07:02:48 -0600 Message-Id: <20171128130248.901-3-eblake@redhat.com> In-Reply-To: <20171128130248.901-1-eblake@redhat.com> References: <20171128130248.901-1-eblake@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Tue, 28 Nov 2017 13:03:25 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PULL 2/2] nbd/server: CVE-2017-15118 Stack smash on large export name X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, vsementsov@virtuozzo.com, "open list:Network Block Dev..." , secalert@redhat.com, qemu-stable@nongnu.org, ppandit@redhat.com, Paolo Bonzini Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Introduced in commit f37708f6b8 (2.10). The NBD spec says a client can request export names up to 4096 bytes in length, even though they should not expect success on names longer than 256. However, qemu hard-codes the limit of 256, and fails to filter out a client that probes for a longer name; the result is a stack smash that can potentially give an attacker arbitrary control over the qemu process. The smash can be easily demonstrated with this client: $ qemu-io f raw nbd://localhost:10809/$(printf %3000d 1 | tr ' ' a) If the qemu NBD server binary (whether the standalone qemu-nbd, or the builtin server of QMP nbd-server-start) was compiled with -fstack-protector-strong, the ability to exploit the stack smash into arbitrary execution is a lot more difficult (but still theoretically possible to a determined attacker, perhaps in combination with other CVEs). Still, crashing a running qemu (and losing the VM) is bad enough, even if the attacker did not obtain full execution control. CC: qemu-stable@nongnu.org Signed-off-by: Eric Blake --- nbd/server.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/nbd/server.c b/nbd/server.c index a81801e3bc..92c0fdd03b 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -386,6 +386,10 @@ static int nbd_negotiate_handle_info(NBDClient *client= , uint32_t length, msg =3D "name length is incorrect"; goto invalid; } + if (namelen >=3D sizeof(name)) { + msg =3D "name too long for qemu"; + goto invalid; + } if (nbd_read(client->ioc, name, namelen, errp) < 0) { return -EIO; } --=20 2.14.3